The increasing architectural demand for functionally diverse configurations has led to the widespread adoption of asymmetric structures, such as T-shaped buildings, which inherently possess plan irregularities. In these structures, the center of mass (CM) and the center of rigidity (CR) do not naturally coincide, leading to significant eccentricity and severe lateral-torsional coupling during seismic events. This study investigates the torsional behaviour and dynamic response of a G+16 multi-story, T-shaped reinforced concrete (RC) building. The structural framework was modelled and analyzed using ETABS software, employing Response Spectrum Analysis (RSA) in compliance with IS 1893: 2016 guidelines for Seismic Zone 3. Critical response parameters, including maximum story displacement, base shear, story drift, and modal time periods, were evaluated to quantify torsional irregularities. The analytical results demonstrated a substantial shift of the CR towards the stiffer flange portion of the building, causing extreme torsional stress and dangerous stress concentrations specifically at the re-entrant corners. Under lateral seismic loading, the drift ratio (D₌₀ₗ/D₀ₕ₆) indicated the presence of extreme torsional irregularities along the Y-direction. To mitigate these vulnerabilities, targeted structural interventions were evaluated; the findings confirm that the strategic placement of shear walls at re-entrant corners or the implementation of seismic joints effectively shifts the CR closer to the CM, thereby optimizing lateral stability and minimizing overall torsional rotation.
Ghorpade Pratik Sahebrao (Fri,) studied this question.